Interventional medicine is the collection of medical procedures in which access to the site of treatment is made by navigation through one of the subject's blood vessels, body cavities or lumens. Interventional medicine technologies have been applied to the manipulation of medical instruments such as guide wires and catheters which contact tissues during surgical navigation procedures, making these procedures more precise, repeatable, and less dependent on the device manipulation skills of the physician. Remote navigation of medical devices is a recent technology that has the potential to provide major improvements to minimally invasive medical procedures. Several presently available interventional medical systems for directing the distal end of a medical device use computer-assisted navigation and a display means for providing an image of the medical device within the anatomy. Such systems can display a projection or image of the medical device being navigated to a target location obtained from an imaging system such as x-ray fluoroscopy or computed tomography; the surgical navigation being effected through means such as remote control of the orientation of the device distal end and proximal advancement of the medical device.
Right-heart catheterization enables pressure and oxygen saturation measure in the right heart chambers, and helps in the diagnosis of tricuspid valve abnormalities. Left-heart catheterization enables evaluation of mitral and aortic valvular defects and myocardial disease. In a typical minimally invasive intervention, data are collected from a catheter or other interventional device that are of great use in treatment planning, guidance, monitoring, and control. In electrophysiology applications, for example, electrical signal measurements are taken at a number of points within the cardiac cavities to map cardiac activity and determine the source of arrhythmias.
The heart beat is regulated by the cardiac pacemaker located in the sinoatrial node; it generates electrical impulses at a typical rate of about 70 per minute. The impulses from the sinoatrial node propagate in a defined sequence to the other structures of the heart, resulting in atrial chambers contractions followed, after a delay of about 0.3 s, by ventricles contractions. Many types of heart disease induce cardiac rhythm disturbances, such as heart-attack-induced ventricular dysrhythmia. Arrhythmias and dysrhythmias disrupt the pumping action of the heart and can lead to cardiac arrest.
There exist a number of mechanisms that disturb the heart rhythm. Arrhythmias can originate from an ectopic focus or center, that may be located at any point within the heart, essentially an abnormally placed secondary pacemaker driving the heart at a higher rate than normal. Disturbances in the cardiac rhythm also originate from the formation of a disorganized electrical circuit, called “re-entry” and resulting in a reentrant rhythm, usually located within the atrium, at the junction between an atrium and a ventricle, or within a ventricle. In a reentrant rhythm, an impulse circulates continuously in a local, damaged area of the heart, causing irregular heart stimulation at an abnormally high rate. Finally various forms of heart block can develop, preventing the normal propagation of the electrical impulses through the heart, slowing down or completely stopping the heart. Heart blocks originate in a point of local heart damage, and can be located within a chamber, or at the junction of two chambers. Examples of clinically classified arrhythmias include paroxysmal or chronic extra-systolic activity, either atrial (mostly benign) or ventricular; auricular flutter, an irregularity of the heartbeat in which contractions of the auricle exceed in number those of the ventricle, atrial fibrillation, an irregular and uncoordinated rhythm of contraction of the atrial muscles; and ventricular tachycardia or fibrillation (rapidly lethal), among other conditions.
Atrial fibrillation is the most common of the major heart rhythm irregularities, and occurs, for example, in spasms following chest surgery, after pulmonary vein embolism, or as a consequence of serious fever or infections. Defects or disease of the mitral valve, when severe enough, will also cause atrial fibrillation, particularly in case of congestive heart failure (when the heart is unable to pump adequate quantities of blood into the body's circulatory system). Continuous atrial fibrillation might lead to the formation of clots and related risks of embolism.
In recent years, the development of minimally invasive techniques has lead to the emergence of intra-cardiac radio-frequency (RF) ablation as a viable alternative of reduced morbidity to surgery for the treatment of most arrhythmias resistant to drug approaches or to treatment via pacemaker or defibrillator approaches. RF ablation aims at eliminating the damaged tissue at the site of ectopic activity centers, or at the elimination of reentrant circuit loops via tissue fulguration. Most ablation treatments rely on anatomical imaging techniques, electrical activity mapping, or a combination of electro-anatomical approaches. RF ablation proceeds by depositing energy to locally raise the tissue temperature to fulguration.
RF ablation is the treatment of choice for most atrial fibrillation cases. The right atrium is relatively easy to access via venous perforation, while left atrium access via an arterial retrograde approach is not practical with today's mechanical navigation systems, due to the number of turns required in accessing the atrium through two valves and the left ventricle. Current mechanical approaches instead access the left atrium through a venous approach to the right atrium, followed by trans-septal wall puncture (typically at the fossa ovalis) into the left atrium.
Circumferential pulmonary vein ablation (CPVA) is an effective treatment for left atrial fibrillation. The ability to understand and correctly reconstruct the left atrial and pulmonary vein anatomy is essential to deploy continuous effective ablation lines around the target regions at the pulmonary vein ostium—left atrial junctions. One of the potential advantages of CPVA over other techniques is the absence of pulmonary vein stenosis. However such an advantage is not always attained by use of ablation relying on an electro-anatomical approach.